This invention relates to test stands including dynamometers for rotary outputs of mechanisms as, for example, vehicles and, more specifically, to couplings utilized for coupling dynamometers to the rotary output of the mechanism where the rotary output is in the form of a sprocket.
Manufacturers of quality mechanical powered vehicles almost invariably test the vehicle prior to releasing the same for sale to ensure that the vehicle is performing properly and is up to its rated capability. In some cases, the testing has been performed with dynamometers, while in others, the testing has been performed by other means.
Dynamometer testing is generally preferred over other forms of testing by reason of increased reliability of test results due to the elimination of subjective judgement on the part of operators and/or observers through the use of measuring apparatus. When dynamometer testing is used, there is a need to, by some means, couple the dynamometer to the rotary output of the vehicle. Dependent upon the type of vehicle, the coupling arrangement is more or less complex because of varying requirements for strength in the coupling. For example, in crawler-type vehicles, where testing is to be performed at the final drive, low rotational speeds and high torque outputs are invariably present requiring a high strength coupling.
Other factors present difficulties in the testing procedure as well as regards couplings. For example, there may be a lack of alignment between the rotary output of the vehicle and the rotary input of the test stand and means must be provided for compensating for such misalignment during the testing procedure without introducing errors of any appreciable magnitude into the test results.
Moreover, because manufacturers may provide a variety of vehicle models, any one or all of which may have rotary outputs which differ from the others in a variety of respects, a difficulty has arisen in adapting the coupling for a change in the testing procedure from one model of vehicle to another.
In the commonly assigned, copending application of Lionel L. Kinney, entitled "Dynamometer And Coupling For A Test Stand", Ser. No. 763,316, filed Jan. 28, 1977, now U.S. Pat. No. 4,092,855, there is disclosed a dynamometer construction which is quite satisfactory for use in test stands whereat crawler-type vehicles are to be tested. However, the Kinney dynamometer requires the use of a pair of spherical couplings in the rotational input for the dynamometer to provide for misalignment between the dynamometer and the vehicle to be tested. Such spherical couplings must necessarily be of high strength due to the high torques involved and, as a consequence, are quite expensive and add considerably to the cost of the dynamometer.
Moreover, in the Kinney construction, when the test stand is to be used for testing differing vehicle models, the coupling (or chuck) which couples the rotational input of the dynamometer to the vehicle must be changed.
In the commonly assigned, copending application of Charles H. Herr, entitled "Dynamometer Test Stand", Ser. No. 816,702, filed July 18, 1977, a dynamometer construction which constitutes an improvement over that disclosed by Kinney is disclosed. The Herr construction eliminates the need for two spherical couplings in the rotational input for the dynamometer and thereby considerably reduces the expense of the assembly. However, like the Kinney dynamometer, the Herr dynamometer is not readily adapted for use in testing a variety of different vehicle models without changing the coupling (or chuck) by which the dynamometer is coupled to the vehicle.
Moreover, the Herr dynamometer construction employs a coupling which shifts on the vehicle output sprocket during testing. It is necessary that sufficient tooth clearance be provided both axially and radially to prevent interference due to maximum misalignment conditions between sprocket shaft axis and dynamometer axis, and manufacturing tolerances on the sprocket. When the conditions of minimum misalignment, minimum sprocket size and low torque occur, this tooth clearance results in some noise, but tests show no detrimental effects on torque reading.